胶结充填体三轴压缩变形破坏及能量耗散特征分析

Characteristic analysis of deformation failure and energy dissipation of cemented backfill body under triaxial compression

充填体的变形破坏、能量耗散与围压的变化密切相关,通过开展不同灰砂配比、浓度的充填体单轴、三轴压缩试验,基于系列试验结果,研究了不同围压加载阶段充填体的变形特征、破坏模式及能量耗散与围压的内在关系。结果表明,随着围压的增加,充填体的峰值应变随之增大,且两者呈线性相关;低围压时充填体呈现脆性破坏,表现为应变软化特征,随着围压增大,充填体由脆性向应变硬化转化,灰砂比越大、浓度越高,充填体发生脆-延性的临界围压值越大。充填体的破坏裂纹发展形式各异,大致可分为单一、平行、交叉和复合4种类型;宏观破坏表现主要呈"X"状、"Y"状剪切模式,破坏面的类型主要分为:直线式光滑摩擦面、圆弧式破碎摩擦面、直线式破碎摩擦面以及台阶式破碎摩擦面。充填体的峰值强度与围压也呈正线性相关,内摩擦角对灰砂比的敏感性要高于浓度。围压的增大能够相当程度上提高充填体各阶段的应变能,峰前、峰后能耗量、单位体积变形能以及总能耗与围压皆呈正相关性。

The deformation failure and energy dissipation of backfill body are closely relative to confining pressure. Experiments are taken to investigate backfill body samples under uniaxial compression and triaxial compression. Based on the experimental results, the internal relations among deformation feature, failure mode, energy dissipation and confining pressure are studied and compared. The results show that the peak strain of backfill body increases with the increase of the confining pressure, and takes a linear correlation. Under a low confining pressure, backfill body has a brittle failure characteristic and presents a strain softening behavior; as the confining pressure increases, the mechanical feature of backfill body performs by a way of transformation from brittleness to strain hardening; the cement/tailing ratio and solid concentration are higher, the critical value of the confining pressure from brittle to ductile is greater. The forms of crack and fracture propagation are diverse, which can be sorted into single type, parallel type, intersection type and complex type. The main macrofailure modes are X-shaped and Y-shaped shear failure. The forms of failure plane are classified by linear smooth friction surface, arc rough friction surface, linear rough friction surface, terrace rough friction surface. The peak strength also increases linearly as the confining pressure increasing. The sensitivity of cohesion to cement/tailing ratio is higher than that of solid concentration. The deformation energy of backfill body at different compressed stages increases to a considerable extent with the increase of confining pressure. The relations of the amount of energy dissipation before yield deformation stage and after yield deformation stage, unit volume strain energy and total energy consumption take a positive proportion of the confining pressures.